In the area of coating or painting of oxidic surfaces, known methods for promoting adhesion involve bifunctional organosilane compounds, for example, which establish a chemical bond between the polymer matrix of the paint and the inorganic substrate. One disadvantage, among others, of these adhesion promoters is that optimal adhesion is ensured only when hydroxide groups with which the silane can interact are present on the surface of the substrate. In many cases, a complicated pretreatment of the substrate is therefore necessary for silanization of surfaces. In addition, the manufacture of customized materials is very complicated, and furthermore, customized materials are not known for all substrates.
Self-assembled monolayers (SAMs, also referred to as self-organizing monolayers) have been investigated and described since 1940, but it was not until 1983 that efforts were begun to make technical use of this organization process.
In principle, self-assembled monolayers have two different active groups, between which a spacer, for example an aliphatic spacer, is present. One group thereof interacts with the surface, and the other end group acts with a specific property or connects to another functional compound. The SAMs form chemical bonds which resist attack by water, and which at the same time are able to prevent all electrochemical reactions at the interlayers. The self-organization of the monomolecular layers on a solid surface provides an efficient method for producing an interlayer having a defined composition, structure, and thickness. Selectively self-organizing adhesion promoters have the advantage that they ensure adhesion of the paint layers and adhesive layers to metallic surfaces for long service lives, which is necessary in the automotive area, for example, for further improvement of the corrosion protection. The self-organizing adhesion promoters also allow consistently good adhesion of a uniform paint layer on the composite materials, which are being increasingly used, and which have different surfaces, such as plastic-metal composite materials.
Self-organizing monolayers are used in semiconductor technology, for example, for surface stabilization and customized functionalization of electrodes. The permeability and the charge transfer rate are influenced, depending on the length of the alkyl chains used. The field of application of self-organizing monolayers is very broad. The technology of the self-organizing monolayer is used, among other things, in the electrochemical scanning tunneling microscope, in cell studies, in sensor systems, and in nanoelectronics. However, production of the SAMs described in the prior art is complicated and costly.
The coupling of an inorganic substrate to biological components for modifying the surface properties is known in biomimetics. Bacteriophages, selected from a phage library, which present short peptides have been used, for example, to precipitate and separate inorganic materials (WO 2003/078451). In addition, hybrid materials composed of an inorganic substrate and specific peptide ligands are used as a potential approach for changing the substrate surface. However, identifying the biological ligand (usually a peptide) which matches the substrate is time- and cost-intensive, and heretofore has precluded a specific application. The concept of a bifunctional ligand for binding two inorganic components is addressed in the prior art. Specifically, the binding of cells or biomolecules to a polymer substrate, in particular an oxidized chlorine-doped polypyrrole (PPyCl) or poly(lactate co-glycolate) (PLGA), by bacteriophages having bifunctional binding properties is described in WO 2004/035612, for example. The further binding to another substance, which like a coating material, for example, is not a biological binding partner of the phage used, is not further described; this binding would likewise have to take place selectively and would require an exact match of the ligand to the further binding component.
Therefore, there is a great need to provide novel compounds which are suitable for use on oxidic surfaces, and which avoid the stated disadvantages of the prior art.
It has surprisingly been found that certain dodecapeptides may advantageously be used as coating agents, adhesion promoters, or adhesives for oxidic surfaces.